This invention relates to watercraft which rely upon a flow of water from an outside supply for cooling marine engines and associated equipment within the watercraft and, more particularly, to an alarm system for providing an early warning of the failure of a marine cooling system.
Watercraft which utilize internal combustion engines for propulsion and/or auxiliary purposes standardly use the water supporting the craft for cooling purposes. Water for circulation within a marine cooling system is pumped via an engine driven water pump up through an open-ended water inlet conduit which extends into the water supporting the craft. The water may be circulated through a water jacket or manifold to absorb heat directly or the water may be circulated through heat exchangers which also receive engine coolant, gear lubricants, transmission fluid or the like for indirect absorbtion of heat. In any event, once the water has absorbed heat generated by the engine, transmission and/or other associated equipment, the water is returned to the body of water supporting the craft typically through an engine exhaust conduit.
All waterways include a certain amount of natural debris such as weeds, leaves, and the like, as well as unnatural debris such as plastic bags, paper, and the like. Accordingly, a coarse strainer is often provided across the open end of the water inlet to prevent large pieces of debris from entering the cooling system. While the coarse strainer prevents large pieces of debris from entering the cooling system, the strainer itself may be partially or totally blocked and prevent the proper flow of cooling water from entering the cooling system water inlet conduit.
Blockage of the strainer resulting in a cessation or severe reduction of the water flow through the water inlet conduit and thereby the marine cooling system eventually causes the marine engine and any associated equipment cooled by the cooling system to overheat. While the engine temperature is ordinarily displayed on a temperature gauge in the craft's cabin, oftentimes the gauge will go unnoticed permitting excessively high temperatures to develop. Such high temperatures can not only ruin the engine, transmission and/or associated equipment cooled by the cooling system but can also start fires and burn holes in the manifold and/or exhaust system, which holes can permit dangerous fumes or water to enter the craft upon further operation. In large inboard boats, packing glands which seal the passage of propeller drive shafts through the hull may also be cooled by the cooling system. Failure of such glands due to overheating can result in sizeable holes surrounding the drive shafts and could sink a boat.
U.S. Pat. Nos. 4,160,733 and 3,864,260 disclose cleaning systems for marine engine cooling water inlets. The cleaning system of the former patent is activated manually or upon the detection of an elevated engine temperature and the cleaning system of the latter patent is activated manually or in response to the activation of a vacuum switch which monitors the vacuum within the water inlet. While these patents appear to present viable cleaning systems, activation of a cleaning system upon detection of an elevated engine temperature may not prevent damage from overheating, and the use of a vacuum switch to monitor the water inlet presents complications and is less than absolutely reliable.
It is thus apparent that the need exists for a reliable, inexpensive, simply constructed early warning system for the detection of failures of marine cooling systems prior to the overheating of a marine engine or associated equipment cooled by the cooling system.